Our major project is the isolation and characterization of the messenger RNAs for collagen. We are using chick embryo tissues for this project and the others mentioned below. Two approaches are being taken for the isolation of these mRNA species. One involves the use of various methods for RNA isolation followed by the assay of the RNA for its ability to direct the synthesis of collagen in a cell-free system derived from wheat germ. The other uses precipitation of collagen-synthesizing polysomes by anti-collagen antibodies. The sizes, poly-A content, stability and other properties of these mRNAs will be investigated. We are also studying how the cell regulates the ratio of alpha 1 to alpha 2 chains that are synthesized. We are also attempting to identify the stage at which disulfide linking of pro alpha chains occurs, and at which the triple helix forms.